How to Use Your DSLR's Autofocus Modes

Still Shot, Tracking Movement, or a Little of Both, There's an AF Mode for That

DSLR Camera
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Most DSLR cameras have three distinct autofocus (AF) modes that are designed to help photographers in different situations. These are useful tools that can be used to improve photographs and it is important to understand the differences between them. 

The various camera manufacturers use different names for each of these modes, yet they all serve the same purpose.

One Shot / Single Shot / AF-S

Single Shot is the autofocus mode that most DSLR photographers use with their cameras, and it is definitely the one to start with as you learn how to use your DSLR.

 It is best to practice in this mode while shooting static photos, such as landscapes or still life.

In Single Shot mode, the camera needs to be re-focused every time you move the camera, and -- as the name suggests -- it will only shoot a single shot at a time.

To use it, choose a focus point and press the shutter button halfway until you hear a beep (if you have the function activated) or notice the focus indicator light in the viewfinder has gone solid. Press the shutter button completely to take the picture and repeat for the next shot.

Note that most cameras will not let you take a photograph in Single Shot mode until the lens has completely focused.

Digital cameras have a red autofocus assist beam that helps the camera find focus in low light conditions. In most DSLRs, this will only work in Single Shot mode. The same is often true for assist beams built into external speedlights.

AI Servo / Continuous / AF-C

The AI Servo (Canon) or AF-C (Nikon) mode is designed to use with moving subjects and is useful with wildlife and sports photography.

The shutter button is half-pressed to activate focusing, as usual, but there won't be any beeps from the camera or lights in the viewfinder. In this Continuous mode, as long as the shutter is half-pressed, you can track your subject as it moves, and the camera will keep re-focusing.

Take some time to play with this mode because it can be tricky to get used to.

The camera will sense the object you want to focus on, then try to predict its movement and focus on where it thinks the subject will go next.

When this mode was first released it did not work very well at all. It has greatly improved in recent years and many photographers have found it extremely helpful. Of course, the higher-end the camera model, the more fine-tuned and accurate Continuous mode will be.

AI Focus / AF-A

This mode combines both of the previous autofocus modes into one convenient feature.

In AI Focus (Canon) or AF-A (Nikon), the camera remains in Single Shot mode unless the subject moves, in which case it automatically switches to Continuous mode. The camera will emit a soft beep once the subject is focused. This can be particularly useful for photographing children, who are inclined to move around a lot!

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